Much of what can be subsumed under the label of political cosmopolitanism argues that some internationalization of political authority is desirable because of the superior capability of international institutions in solving transnational problems. Surprisingly, however, few scholars have asked whether ordinary citizens share this way of thinking. To address this question, falsifiable hypotheses about the quality and scope conditions of such a public political cosmopolitanism are derived from the literature and tested using the results of a representative survey of German citizens. I show that there is significant support for what I call the interdependence model of cosmopolitan politicization: German citizens' perception of transnational interdependencies (in terms of functional sensitivity as well as moral commitments) fosters beliefs in the capability of international institutions to solve problems. This model has significant explanatory power over different levels of education, and thus disproves a common claim that cognitive mobilization is a crucial scope condition of cosmopolitan politicization. Remarkably, however, the relationships specified by the interdependence model are only marginally moderated by German citizens' sense of their own vulnerability, i.e. their beliefs that the national government is incapable of solving such problems.